Support arcs in Break Track.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/16712

pcbnew/router/pns_line_placer.cpp

@@ -2,7 +2,7 @@
  * KiRouter - a push-and-(sometimes-)shove PCB router
  *
  * Copyright (C) 2013-2017 CERN
- * Copyright (C) 2016-2023 KiCad Developers, see AUTHORS.txt for contributors.
+ * Copyright (C) 2016-2024 KiCad Developers, see AUTHORS.txt for contributors.
  * Author: Tomasz Wlostowski <tomasz.wlostowski@cern.ch>
  *
  * This program is free software: you can redistribute it and/or modify it
@@ -767,7 +767,7 @@ bool LINE_PLACER::rhWalkOnly( const VECTOR2I& aP, LINE& aNewHead, LINE& aNewTail
     // (now a hull or a walk/shove line cannot collide with the 'owner' of the hull under any circumstances).
     // This, however, introduced a subtle bug. For a row/column/any other 'regular' arrangement
     // of overlapping hulls (think of pads of a SOP/SOIC chip or a regular via grid), walking around may
-    // produce a new 'head' that is not considered colliding (due to the clearance epsilon), but with 
+    // produce a new 'head' that is not considered colliding (due to the clearance epsilon), but with
     // its start point inside one of the subsequent hulls to process.
     // We can't have head[0] inside any hull for the algorithm to work - therefore, we now consider the entire
     // 'tail+head' trace when walking around and in case of success, reconstruct the
@@ -932,7 +932,7 @@ bool LINE_PLACER::rhShoveOnly( const VECTOR2I& aP, LINE& aNewHead, LINE& aNewTai
     {
         newHead.AppendVia( makeVia( newHead.CPoint( -1 ) ) );
         PNS_DBG( Dbg(), AddPoint, newHead.Via().Pos(), GREEN, 1000000, "shove-new-via" );
-        
+
     }
 
     SHOVE::SHOVE_STATUS status = m_shove->ShoveLines( newHead );
@@ -1292,6 +1292,38 @@ bool LINE_PLACER::SplitAdjacentSegments( NODE* aNode, ITEM* aSeg, const VECTOR2I
 }
 
 
+bool LINE_PLACER::SplitAdjacentArcs( NODE* aNode, ITEM* aArc, const VECTOR2I& aP )
+{
+    if( !aArc )
+        return false;
+
+    if( !aArc->OfKind( ITEM::ARC_T ) )
+        return false;
+
+    const JOINT* jt = aNode->FindJoint( aP, aArc );
+
+    if( jt && jt->LinkCount() >= 1 )
+        return false;
+
+    ARC*             a_old = static_cast<ARC*>( aArc );
+    const SHAPE_ARC& o_arc = a_old->Arc();
+
+    std::unique_ptr<ARC> a_new[2] = { Clone( *a_old ), Clone( *a_old ) };
+
+    a_new[0]->Arc().ConstructFromStartEndCenter( o_arc.GetP0(), aP, o_arc.GetCenter(),
+                                                 o_arc.IsClockwise(), o_arc.GetWidth() );
+
+    a_new[1]->Arc().ConstructFromStartEndCenter( aP, o_arc.GetP1(), o_arc.GetCenter(),
+                                                 o_arc.IsClockwise(), o_arc.GetWidth() );
+
+    aNode->Remove( a_old );
+    aNode->Add( std::move( a_new[0] ), true );
+    aNode->Add( std::move( a_new[1] ), true );
+
+    return true;
+}
+
+
 bool LINE_PLACER::SetLayer( int aLayer )
 {
     if( m_idle )

pcbnew/router/pns_line_placer.h

@@ -2,7 +2,7 @@
  * KiRouter - a push-and-(sometimes-)shove PCB router
  *
  * Copyright (C) 2013-2017 CERN
- * Copyright (C) 2016-2021 KiCad Developers, see AUTHORS.txt for contributors.
+ * Copyright (C) 2016-2024 KiCad Developers, see AUTHORS.txt for contributors.
  *
  * @author Tomasz Wlostowski <tomasz.wlostowski@cern.ch>
  *
@@ -206,11 +206,17 @@ public:
     void GetModifiedNets( std::vector<NET_HANDLE>& aNets ) const override;
 
     /**
-     * Check if point \a aP lies on segment \a aSeg. If so, splits the segment in two, forming a
+     * Snaps the point \a aP to segment \a aSeg. Splits the segment in two, forming a
      * joint at \a aP and stores updated topology in node \a aNode.
      */
     bool SplitAdjacentSegments( NODE* aNode, ITEM* aSeg, const VECTOR2I& aP );
 
+    /**
+     * Snaps the point \a aP to arc \a aArc. Splits the arc in two, forming a
+     * joint at \a aP and stores updated topology in node \a aNode.
+     */
+    bool SplitAdjacentArcs( NODE* aNode, ITEM* aArc, const VECTOR2I& aP );
+
 private:
     /**
      * Re-route the current track to point aP. Returns true, when routing has completed

pcbnew/router/pns_router.cpp

@@ -1039,13 +1039,20 @@ void ROUTER::SetInterface( ROUTER_IFACE *aIface )
 }
 
 
-void ROUTER::BreakSegment( ITEM *aItem, const VECTOR2I& aP )
+void ROUTER::BreakSegmentOrArc( ITEM *aItem, const VECTOR2I& aP )
 {
     NODE *node = m_world->Branch();
 
     LINE_PLACER placer( this );
 
-    if( placer.SplitAdjacentSegments( node, aItem, aP ) )
+    bool ret = false;
+
+    if( aItem->OfKind( ITEM::SEGMENT_T ) )
+        ret = placer.SplitAdjacentSegments( node, aItem, aP );
+    else if( aItem->OfKind( ITEM::ARC_T ) )
+        ret = placer.SplitAdjacentArcs( node, aItem, aP );
+
+    if( ret )
     {
         CommitRouting( node );
     }

pcbnew/router/pns_router.h

@@ -150,7 +150,7 @@ public:
     bool Finish();
     bool ContinueFromEnd( ITEM** aNewStartItem );
     bool FixRoute( const VECTOR2I& aP, ITEM* aItem, bool aForceFinish, bool aForceCommit );
-    void BreakSegment( ITEM *aItem, const VECTOR2I& aP );
+    void BreakSegmentOrArc( ITEM *aItem, const VECTOR2I& aP );
 
     std::optional<VECTOR2I> UndoLastSegment();
     void CommitRouting();

pcbnew/router/router_tool.cpp

@@ -1563,8 +1563,11 @@ bool ROUTER_TOOL::RoutingInProgress()
 
 void ROUTER_TOOL::breakTrack()
 {
-    if( m_startItem && m_startItem->OfKind( PNS::ITEM::SEGMENT_T ) )
-        m_router->BreakSegment( m_startItem, m_startSnapPoint );
+    if( !m_startItem )
+        return;
+
+    if( m_startItem->OfKind( PNS::ITEM::SEGMENT_T | PNS::ITEM::ARC_T ) )
+        m_router->BreakSegmentOrArc( m_startItem, m_startSnapPoint );
 }
 
 
@@ -2501,7 +2504,7 @@ int ROUTER_TOOL::InlineBreakTrack( const TOOL_EVENT& aEvent )
     const BOARD_CONNECTED_ITEM* item =
             static_cast<const BOARD_CONNECTED_ITEM*>( selection.Front() );
 
-    if( item->Type() != PCB_TRACE_T )
+    if( item->Type() != PCB_TRACE_T && item->Type() != PCB_ARC_T )
         return 0;
 
     m_toolMgr->RunAction( PCB_ACTIONS::selectionClear );
@@ -2516,6 +2519,8 @@ int ROUTER_TOOL::InlineBreakTrack( const TOOL_EVENT& aEvent )
     m_gridHelper->SetUseGrid( gal->GetGridSnapping() && !aEvent.DisableGridSnapping()  );
     m_gridHelper->SetSnap( !aEvent.Modifier( MD_SHIFT ) );
 
+    controls()->ForceCursorPosition( false );
+
     if( toolManager->IsContextMenuActive() )
     {
         // If we're here from a context menu then we need to get the position of the